Ospf Default Passive Interface

[culpri21]

Hi Folks,

Labbed it quickly & i wondered if it's possible to set interfaces to no passive-interface vlan51 for example and then do a default passive-interface. I found that I couldn't do this without effectively configuring default passive-interface and then doing a no passive on the interfaces that are legit VLANs allowed OSPF transits. Goal here is to minimise disruptions!

Thanks in advance

[MHM Cisco World]

Yes you are correct

""I found that I couldn't do this without effectively configuring default passive-interface and then doing a no passive on the interfaces that are legit VLANs allowed OSPF transits""
this correct for L3SW in router we can add no passive-interface under ospf process in L3SW we need to add no passive under VLAN SVI

MHM

[liviu.gheorghe]

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Goal here is to minimise disruptions!

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In this case, maybe it's better to configure each default interface individually under the routing process.

[Blue_Bird]

Hello culpri21,

router ospf 1

passive-interface default
no passive-interface Vlan202
no passive-interface Vlan203

First, you use passive-interface default then all interfaces will be passive. If you want to disable it for one or more specific interfaces to allow ospf transits, you can use the no passive-interface fa0/0 command or  for svi, no passive-interface vlan_id under the OSPF process. 

Instead of giving passive-interface default  command you can use  passive-interface fa0/0 or  passive-interface vlan_id  to directly enable passiving interface on specific interfaces...to block ospf transits.

router ospf 1

 passive-interface Vlan202
passive-interface Vlan203

Best regards
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